Study of linear and non-linear optoelectronic properties of thermally grown thin films of amorphous selenium doped with graphene, multiwalled carbon nanotubes, and silver nanoparticles

The present research covers the impact of doping of different nano-materials [Graphene, Multiwalled Carbon Nanotubes (MWCNTs), and Silver nanoparticles (Ag: NPs)] on the optoelectronic properties of selenium glass. For this, we have prepared the amorphous thin films (ATFs) of pure selenium and nano-additives doped Se and the systematic optical characterization of ATFs of as-prepared samples has been done. We have examined the optical characteristics of prepared ATFs by collecting the experimental spectral data of reflection/transmission in the range of 400 nm to 2500 nm. Knowing the spectral variation of the dispersion parameters, we have calculated the values of the optical band gap Egopt and Urbach tail Ee. The indirect optical transition is found in the present samples that are confirmed by the transition power factor m. The values of real component (i.e., ε') and imaginary components (i.e., ε″) of the dielectric constant and its value in the high-frequency range (i.e., ε∞), as well as single-oscillator dispersion parameters, are also determined. The value of infinite dielectric constant (ε∞) of ATF of parent selenium (ε∞ = 2.65) is increased significantly after the doping of graphene (ε∞ = 3.82), MWCNT (ε∞ = 4.37), and Ag: NPs (ε∞ = 6.19). Further, we have investigated the dependence of tan δ (dissipation factor), τ (relaxation time), optical/electrical conductivities, and volume/surface energy loss functions on photon energy hν. The nonlinear properties of the samples are discussed in terms of their susceptibility and nonlinear refractive index.